The present invention relates to a method and an apparatus for controlling rolling mills, and, more particularly to a method and an apparatus for controlling rolling mills suitable for preventing the zigzagging or snake motion of a material to be rolled.
The reduction ratio for operation and driving sides, or right and left sides, of the material being rolled in the rolling mill often develops an error due to the difference in hardness between the right and left sides of the material or the difference in roll gap between the value at the right and left sides of the material, with the result that the biting position of the material into the roll nip is displaced in the transversal direction of the material and the material to be rolled is curved in its longitudinal direction in what is called the snake or zigzagging phenomenon.
In the event that this nake or zigzagging phenomenon is considerable, the material being rolled is greatly displaced to one side, thereby leading to an excessive partial reduction of the material. This phenomenon may seriously damage or break the reduction rolls or input guide, often causing a great amount of material loss and/or time loss. Even in the case where the snake or zigzagging motion is not considerable, it is necessary to cut the ends of the curved portion of the material in the next step of operation to attain the same material width, thus reducing the product yield.